1. Field of the Invention
The present invention relates to a power-assisted steering system for motor vehicles in the form of a rack-and-pinion steering system.
2. Description of Related Art
Such power-assisted steering systems have a steering rack, which is supported so as to be longitudinally displaceable in a steering gear housing and is provided at either end with a track rod tap. The track rods are generally connected by a screw thread and a ball joint to the steering rack. The steering rack, the screw thread and the ball joint are protected from dirt by means of bellows, which are fastened by one end to the track rod and by the other end to the steering gear housing. In the course of a steering movement the volume enclosed by the bellows varies, with the result that the air quantity contained there has to be compensated. For said purpose, in the known power-assisted steering systems a line is provided between the two air volumes arising on the left and right of the rack-and-pinion steering system, thereby enabling a compensation between the two volumes on either side of the rack-and-pinion steering system. Said line is realized either or by means of a longitudinal bore in the steering rack optionally combined with traverse bores or by means of a separate rigid line on the outside of the steering gear housing or bellows.
The construction outlay for provision of said connection is in practice relatively high. On the other hand, in the absence of such a connection some other way of removing the displaced air volume and/or supplying the necessary air volume is required.
The object of the present invention is therefore to provide a power-assisted steering system for motor vehicles, in which the volumes enclosed by the bellows may be separately varied and/or compensated.
Said object is achieved by a device having the features of claim 1 as well as by a device having the features of claim 6.
Advantageous developments of the invention are described in the sub-claims.